Particle size characterization and sources of sediments in the Uzhumqin sand dunes

Sediment constitutes the fundamental basis for forming and evolving aeolian geomorphology.The characteristics of sediment particle size offer insights into the development and evolution of sandy terrain,making their study critical to understanding aeolian geomorphology and sand control.In this study,we combined high-density collection of surface sediments in the Uzhumqin sand dunes and GIS spatial analysis to analyze the particle size parameters and changes in the spatial distribution of surface sediments in this region.In addition,we used an end-member analysis to identify the potential sources of the sediments.The results showed that surface sediments in the Uzhumqin sand dunes had distinct spatial distributions.Medium and coarse grain sands dominated the sediments in the dunes,and the mean grain size and the sorting coefficient generally increased along the prevailing wind direction,with high values in individual areas related to factors such as material sources and vegetation cover.Skewness was strongly influenced by factors such as landform change and human activity,and spatial variability became more complex.Kurtosis and the soil fractal dimension showed generally decreasing trends along the prevailing wind direction.With dune fixation,the contents of clay and powder particles in the soil increased;the mean particle size,the sorting coefficient,and the fractal dimension of the soil gradually increased,and the skewness and kurtosis gradually decreased.The end-member analysis results indicated the existence of five end-members(EM)in the dune sediments.EM 1 was a mixed component of wind-deposited fine sands and nearby fluvial sediments.EM 2 was the main component of sediments in the study area and was the result of sorting lake sediments by wind action and by the local topography.EM 3 may be a product of river flood deposition.EM 4 and EM 5 had coarser grain sizes.EM 4 was a lake-phase sediment product influenced by topographic and vegetation cover factors,and EM 5 was primarily a river and lake sediment product modified by weathering.The sediment particle size results from the study area indicate that the sediment in the sandy region is generally coarse due to multiple factors,including topography,climate,hydrology,and human activity.Sandy material in the study area originated from nearby,with very little sand being transported from long distances.

The difference analysis of physical-mechanical properties of sediments in the central South Yellow Sea and Zhe-Min coastal area in China

The difference analysis of physical-mechanical properties of muddy sediments is made in the central South Yellow Sea and the Zhe-Min（Zhejiang Province to Fujian Province of China） coastal area. The results show that sediments in the two regions are both dominated by mud. There are perfect negative power function correlations between the water content and the density, the compression coefficient and the compression modulus; a good positive power function correlation between the liquid limit and the plastic limit, a perfect positive linear correlation between the water content and the void ratio, and a perfect polynomial function correlation between the miniature vane shear strength and the pocket penetration resistance. In general, compared with sediments in the Zhe-Min coastal area, sediments in the central South Yellow Sea possess high water content, high void ratio,low density, high plasticity, high compressibility, low shear strength. The causes of the differences between physical-mechanical properties of sediments are analyzed from the topographic features, material sources,hydrodynamic conditions, deposition rate, and material composition. Compared with the Zhe-Min coastal area,the central South Yellow Sea is far from the Mainland and low-lying; has poor hydrodynamic condition; the materials diffused to the area are less and dominated by fine clay, have the high content of smectite and organic matters. These factors lead to sediments of the central South Yellow Sea has the higher water content, the higher plasticity, the lower density, and the lower strength than sediments in the Zhe-Min coastal area.

Morphodynamics and sediment connectivity index in an unmanaged,debris-flow prone catchment:a through time perspective

Torrential processes are among the main actors responsible for sediment production and mobility in mountain catchments.For this reason,the understanding of preferential pathways for sediment routing has become a priority in hazard assessment and mitigation.In this context,the sediment Connectivity Index(IC)enables to analyse the existing linkage between sediment sources and the selected target(channel network or catchment outlet).The IC is a grid-based index that allows fast computation of sediment connectivity based on landscape information derived from a single Digital Terrain Model(DTM).The index computation is based on the log-ratio between an upslope and a downslope component,including information about drainage area,slope,terrain roughness,and distance to the analysis target(e.g.outlet).The output is a map that highlights the degree of structural connectivity of sediment pathways over analysed catchments.Until now,these maps are however rarely used to help defining debris-flow hazard maps,notably due to a lack of guidelines to interpret the IC spatial distribution.This paper proposes an exploitation procedure along profiles to extract more information from the analysis of mapped IC values.The methodology relies on the analysis of the IC and its component variables along the main channel profile,integrated with information about sediment budgeting derived from Difference of DEMs(DoD).The study of connectivity was applied in the unmanaged sub-catchment(without torrent control works)of the Rio Soial(Autonomous Province of Trento–NE Italy)to understanding the geomorphic evolution of the area after five debris flows(in ten years)and the related changes of sediment connectivity.Using a recent DTM as validation,we demonstrated how an IC analysis over the older DTM can help predicting geomorphic changes and associated hazards.The results show an IC aptitude to capture geomorphic trajectories,anticipate debris flow deposits in a specific channel location,and depict preferential routing pathways.

汛期与非汛期水沙条件对黄河下游不同河段过流能力的影响

20世纪80年代以来黄河下游水沙输移特性显著改变,下游河道经历强来沙作用下的持续淤积与小浪底水库调控下的持续冲刷过程。基于黄河下游1986—2020年实测水沙数据与固定断面地形,计算了河段尺度的平滩流量,量化了汛期与非汛期水沙过程对各河段过流能力的相对贡献。结果表明:①小浪底枢纽运行前水流冲刷强度随时间减弱,下游河道呈汛期淤积、非汛期冲刷的整体淤积态势,平滩流量持续减小,最小过流能力小于2000 m^(3)/s。②小浪底枢纽运行后水流冲刷强度显著增大,尤其在非汛期,对河床冲刷产生重要影响;各河段过流能力显著恢复,其中游荡段恢复最为迅速。③各河段平滩流量与前5 a汛期、非汛期平均水流冲刷强度呈良好的幂律关系,该关系能较好地反映汛期与非汛期累积水沙过程对过流能力的综合影响。④小浪底枢纽运行后,非汛期水沙条件对平滩流量的贡献率增大,尤其是对游荡段具有重要影响(占比53%),对过渡段与弯曲段贡献则较小(占比不到20%)。

不同条件下高速剪切均质和高压均质对红景天复合饮料的影响

基于CiteSpace软件可视化分析及结合实际情况下复合饮料极易产生沉淀问题,该研究发现高速剪切均质和高压均质均能降低饮料的沉淀,但不同的均质方式对饮料的影响不同。以粒径、沉淀率、稳定系数、色差值、L^(*)和感官评分为指标,在不同参数条件下采用高压均质和高速剪切均质对复合饮料进行均质,选取最优的均质方法。结果表明,虽然高压均质和高速剪切均质均能明显提高饮料的稳定性,但经高压均质后的饮料色泽过于暗沉。而采用均质转速为12500 r/min,均质次数为2次的高速剪切均质的方式对复合饮料进行均质后,饮料的稳定性升高的同时,色泽鲜艳明亮,呈鲜艳的暖橙色,使人食欲感增强,感官评分也较高。故均质转速为12500 r/min,均质次数为2次的高速剪切均质的方式更适用于复合饮料,其作用效果也较好。研究结果可为后续饮料均质提供一定的参考。

福宁湾及附近海域悬沙粒度与影响因素

基于闽北福宁湾及附近海域冬、夏两季水文泥沙实测数据,分析了不同时间尺度下悬沙的粒度特征,探讨了影响悬沙粒度季节差异的主要因素以及悬沙粒度与浓度的关系。结果表明:正常天气下,研究区悬沙中值粒径普遍大于6.5Φ。悬沙粒度具有“冬细夏粗”的季节分布特征;受潮动力影响,悬沙粒度大小潮变化明显;潮周期内悬沙粒径变化规律不明显。悬沙粒级-标准偏差曲线显示两种主要的敏感粒级分布范围为2.8~3.4μm和21.1~25.1μm。悬沙粒度“冬细夏粗”的季节差异主要受底质再悬浮和泥沙来源的影响。冬季悬沙粒径与浓度的相关性不明显,夏季两者存在显著的线性关系,悬沙粒径随悬沙浓度的增加而减小,这种季节差异可能与悬沙来源和混合作用有关。夏季悬沙粒径的粗化可能与细颗粒发生絮凝沉降有关。

林下三七不同管理措施对坡面产流产沙和土壤特性的影响

[目的]揭示不同管理措施对三七[Panax notoginseng(Burkill)F.H.Chen]林地产流产沙和土壤特性的影响,为科学防控林下三七种植的水土流失提供理论依据。[方法]采用野外径流小区原位观测试验,于2022年雨季对不同坡度(5°,10°,15°)自然林地(CK)、林下整地(SP)、无棚三七林地(NC)、有棚三七林地(HC)的产流产沙量进行量化,探究不同管理措施对三七林地坡面产沙产流及土壤特性的影响。[结果](1)2022年寻甸县降雨总量为1031.70 mm,属平水年份。林外和林内累计侵蚀性降雨量分别为845.40,565.60 mm,林冠截留率为9.97%~67.38%。(2)各管理措施三七林地产流产沙存在极显著差异(p<0.01)。与CK相比,SP、NC和HC平均总径流量分别增加272.23%,171.19%和106.89%,平均总产沙量分别增加385.15%,248.82%和138.84%;三七林地布设雨棚有较好的减沙效果。(3)CK、SP的土壤特性分别与其他管理措施三七林地土壤特性存在显著差异;NC和HC的平均几何直径和土壤抗冲系数存在显著差异(p<0.05),其他土壤特性无显著差异;主成分分析显示,不同管理措施三七林地土壤饱和导水率、枯落物储量、土壤体积质量和K值对产流产沙的影响较大。(4)各管理措施三七林地次降雨产流产沙量和降雨量或降雨侵蚀力与降雨强度之间呈显著幂函数关系(p<0.05);总径流量和总产沙量与坡度呈极显著指数关系(p<0.01),R^(2)>0.90;且产流产沙量随着坡度增加,流失增幅越大。[结论]林下整地和林下种植三七导致水土流失显著增加,但最大土壤流失量[34.53 t/(km^(2)·a)]远低于西南岩溶区土壤容许流失量。建议在缓坡林地种植三七,且可通过搭建遮雨棚和改善土壤特性来缓解水力侵蚀。

海南海口美舍河国家湿地公园沉积物时空分布特征及其影响因素

了解湿地生态系统沉积物理化性质及重金属分布特征有利于湿地公园科学管理和保护,对于维持区域生态平衡也具有重要意义。研究选取海南海口美舍河国家湿地公园不同河段沉积物为研究对象,连续4年(2018年-2021年)进行采样检测,探究不同年份、不同河段间沉积物理化性质和重金属时空分布特征,并分析其主要影响因子,结果表明河段位置是造成沉积物理化性质及重金属分布差异的主要原因。美舍河沉积物有机碳含量范围为14.06g/kg~56.15g/kg,下游(和平桥)沉积物有机碳含量显著高于中游(国兴桥)和上游(沙坡水库);从不同年份看,中游沉积物有机碳含量变化为2018年<2019年<2021年<2020年,其余河段变化不明显,沉积物有机碳分布主要受到pH、铅、全氮、全磷的影响。沉积物全氮全磷含量变化一致,在所有年份均表现为下游>中游>上游。沉积物重金属含量(铜、铅、锌)4年间在不同河段变化较为一致,下游重金属富集作用较强,铜、铅、锌含量均显著高于上游河段,沉积物pH、全磷、有机碳是影响其分布的主要理化因子。研究结果反映了不同河段湿地的质量和健康程度,有助于湿地生态系统的可持续发展和保护。

煤顶板覆岩沉积环境区域性研究

在煤矿开采活动中,顶板覆岩的沉积环境对煤层顶板的稳固性及作业安全性具有直接影响。作为矿区工作面的主要支撑结构,顶板覆岩的岩性、厚度和组合特征决定了顶板的稳定性,进而影响着矿井的安全性和采矿效率。随着开采深度与规模的不断扩展,煤层顶板覆岩的沉积特征及分布规律成为矿区地质研究的重点课题。在不同地质构造和沉积背景之下,煤层顶板覆岩的特征常表现出显著的区域差异,系统地研究其沉积环境具有重要的意义。文中选择延安组与安定组地层展开分析,通过岩心观察、沉积学分析与测井数据的多维度融合,试图深入探讨煤层顶板覆岩的沉积环境特征,揭示其横向与纵向的变化规律,以期为煤矿开采工程的安全设计提供科学支持。

盾构排浆管道内块石流速分析与沉积临界泥浆流速公式推导

为了明晰排浆管道内各种块石的流速情况,探讨块石沉积形成的管道堵塞和泥浆流速的关系,首先,根据流体力学基本方程推导出泥浆液动力计算式;然后,从运动力学角度对水平、斜向上、斜向下、垂直向上管道内的石块取最难排出的状态进行受力分析;最后,对不同形状、不同粒径石块,在不同倾斜角度的泥浆通道内随泥浆流动,达到受力平衡时和泥浆流速差值计算公式进行推导,进而分析推导出各种块石沉积临界泥浆流速计算公式,并设定工程数据试算。得出以下结论:1)不同尺寸、不同形状、不同密度的块石在不同倾角排浆管道内差速流动、流动速度自动分级、沉积临界泥浆流速不同;2)密度小、体积小的块石运动速度快、沉积临界泥浆流速小;3)相同重量、密度的块石,球形的运动速度最快、沉积临界泥浆流速最小,正方体形的次之,长条形的运动速度最慢、沉积临界泥浆流速最大,长径比越大流速越慢、沉积临界泥浆流速越大;4)同一块石,在向下管道流速最快、沉积临界泥浆流速最小,水平管道次之,在垂直上升管道流速最小、沉积临界泥浆流速最大。重点控制始发井和地面垂直向上管道内的泥浆流速至关重要。通过计算以适用经济的泥浆流速来预防排泥管道堵塞。

Environmental change inferred from Rb and Sr of lacustrine sediments in Huangqihai Lake,Inner Mongolia

Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investigates the record of palaeolake stand state, sedimentary environmental evolution,and winter monsoon change.First,these samples are separated into three different grain size fractions,i.e.,total sediments,77-20μm and〈20μm. Second,the chemical elements-Rb and Sr-of the grain size separation were tested and analyzed systematically in this paper.Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument,respectively.The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company.The results showed the elements and the ratios varied regularly with the grain size.But the ratio of Rb/Sr in the sediments〈20μm correlates positively with the magnetic susceptibility of these samples.Therefore,the ratio of Rb/Sr in the fraction〈20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites.It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment.

Iron and inorganic carbon in Liaodong Gulf sediments of Bohai Sea in China

Iron in seawater is an essential trace metal for phytoplankton that plays an important role in the marine carbon cycle. But most studies focused on oceanic iron fertilization in high nutrient low chlorophyll （HNLC） seawaters. A study of inorganic carbon （IC） forms and its influencing factors was presented in Liaodong Gulf sediments, and especially the influence of iron was discussed in detail. Inorganic carbon in Liaodong Gulf sediments was divided into five forms： NaCl, NH3·H2O, NaOH, NH2OH·HCl and HCl. The concentration of NaCl and NaOH forms were similar and they only occupied the minority of total inorganic carbon （TIC）. However, NH3 ·H2O, NH2OH · HCl and HCl forms were the principal forms of TIC and accounted for more than 80% of TIC. Especially, the percentage of NH3·H2O form was much higher than that in the Changjiang River Estuary and Jiaozhou Bay sediments. All forms of inorganic carbon were influenced by organic carbon, pore water, iron, pH, redox potential （Eh） and sulfur potential（Es） in sediments, moreover, the influences had different characteristics for different IC forms. However, the redox reactions of iron affected mainly active IC forms. Iron had little effect on NH2OH· HCl and HCl forms of IC which were influenced mainly by pH. Iron had a stronger influence on NaCl, NaOH and NH3· H2O forms of IC ; the influence of Fe^2＋ was higher than Fe^3＋ and its effect on NH3 ·H2O form was stronger than on NaCl and NaOH forms.

Forms and functions of inorganic carbon in the Jiaozhou Bay sediments

Inorganic carbon forms and their influencing factors, mutual transformation and contribution to carbon cycling in the Jiaozhou Bay sediments were discussed. The results show that inorganic carbon in sediments could be divided into five forms： NaCl form, NH3-H20 form, NaOH form, NH20H-HCl form and HCI form. Thereinto, NH2OH.HCl form and HCl form account for more than 70% of total inorganic carbon. There was close relationship among every form of inorganic carbon and their correlativity was clearly different with different sedimentary environment except the similar strong positive correlation among NH-OH-HCl form, HCl form and total inorganic carbon in all regions of the Jiaozhou Bay. All forms of inorganic carbon were influenced by organic carbon, pH, Eh, Es, nitrogen and phosphorus in sediments, but their influence had different characteristics in different regions. Every form of inorganic carbon transformed into each other continuously during early diagenesis of sediments and the common phenomenon was that NaCl form, NH3-H2O form, NaOH form and NH2OH-HCl form might transform into steady HCl form. NaCl form, NH3-H2O form, NaOH form and NH2OH-HCl form could participate in carbon recycle and they are potential carbon source; HCl form may be buried for a long time in sediments, and it may be one of the final resting places of atmospheric C02. Inorganic carbon which entered into sediments was about 4.98× 1010 g in the Jiaozhou Bay every year, in which about 1.47×1010 g of inorganic carbon might be buried for a long time and about 3.51 × 1010 g of inorganic carbon might return into seawater and take part in carbon recycling.

Differences on Condition and Mechanism of Potash Deposited in O2 m5-6 Subsection of Northern Shaanxi Salt Basin

The Northern Shaanxi salt basin locates in the east of the Ordos basin.In this area,the thick layer salt sediment exists in the Majiagou Formation of Ordovician.Especial in the sixth subsection of the Majiagou fifth member,it

明渠含沙水流流量测量精度分析——以超声时差法测流为例

水流中泥沙的存在对流量测量精度的影响一直是水力学的重要问题。本文以超声时差法测流方法为例,在室内明渠水槽中开展了不同含沙量(最大含沙量27 kg·m^(-3),宁夏引黄灌区天然沙,中值粒径0.015 mm)对流量测量精度的影响测试研究,以电磁流量计及巴歇尔槽测量值为基准,对比了超声时差法在不同含沙量下的流量测量偏差,分析了含沙量对其流量测量精度的影响。结果表明:在含沙条件下,超声时差法的流量测量值总体偏大,且偏差量随含沙量增大呈增大趋势。多声路箱式超声时差流量计受含沙量影响相对较小,在本文泥沙粒径、含沙量范围内平均意义上流量测量偏差在7%;单声路超声时差流量计受含沙量影响较大,在本文测验环境下其在含沙量较高时测量值偏大300%~500%,基本处于失效状态。

2012-2021年长江源区水沙变化特征调查分析

长江源区地处青藏高原,气候条件恶劣,受技术条件限制,有关江源地区河流径流输沙资料较少。为了探究江源地区河流径流输沙情况,基于2012—2021年间水文站实测资料和14个野外观测点数据,分析了长江源区河流水沙时空变化特征。结果表明:①长江源区径流量与降水量、温度显著相关,输沙量与径流量相关系数达0.842,与降水量相关系数为0.610;②受气温、降水等因素影响,长江源区河流径流输沙呈现明显的空间分布差异,其中2018年、2020年、2021年同期流量较大,含沙量则在2019年6月最大;③长江源区各考察点悬沙中值粒径总体呈现增大趋势,床沙中值粒径普遍较大,通天河干流、布曲、尕尔曲床沙中值粒径最大,各河段年际间变化规律不一致。研究成果可对无资料地区河流的径流输沙规律认识提供参考,为长江源区河流保护提供技术支撑。

乌珠穆沁沙地主要风沙环境特征及形成机制研究

厘清区域风沙运动环境和沉积物粒度特征是研究风沙流的关键,对地区风沙灾害的防护与治理具有重要意义。本文利用乌珠穆沁沙地的风况数据,研究沙地起沙风况和输沙势变化特征,同时结合沉积物粒径数据,揭示该地区风沙环境的空间分异规律。结果表明:(1)乌珠穆沁沙地年均起沙风频率为33.8%,平均风速介于3.34~5.40 m·s^(-1)之间,平均起沙风速介于6.46~8.49 m·s^(-1)之间,沙地起沙风频率和风速北部大于南部,西部大于东部。(2)沙地整体年内起沙风频率和风速春季最高,起沙风向以西南方向为主,WSW风向频率最高。(3)沙地输沙势为19.2~193.7 VU,整体属低风能环境,风况多为锐双峰风况,沙地输沙势北部大于南部,西部大于东部。全年沙物质整体向东、东北方向输移,春季是最主要的风沙活动期。(4)沙地整体以粗沙和中沙组分为主,南部和西部土壤粒径偏粗,东部偏细。沙地北部和东部沉积物分选性较差,粒径组分受外来影响较大。总体而言,沙地北部风沙活动最强,适宜人工建植或铺设沙障固沙。沙地东部栽植防护林,避免沙物质持续东移。

模拟降雨条件下不同草本植被对产流产沙的影响

为了探讨不同草本植被对坡面产流产沙的影响,在人工模拟降雨条件下,选择福禄考、佛甲草、蓝羊茅,设计坡度为10°;早熟禾、黑麦草、高羊茅,设计坡度分别为5°、10°、15°,进行试验研究。研究结果表明:不同草本植物均能有效降低土壤的产沙量与产流量,起到保持水土、修复生态的作用。相同草本,不同坡度下,坡度越大,产流、产沙、土壤侵蚀量越大,作用系数也越大。

玛纳斯湖滨岸带盐类和风成砂混合沉积特征及环境意义:来自物理模拟实验的启示

基于对玛纳斯湖现代沉积观察所获得的湖泊内砂岩为风成沉积的初步认识,在滨岸带盐类与风成砂混合沉积基本特征表述的基础上,结合物理模拟实验,分析了其成因过程,再现了风成砂与盐类的混合沉积形成过程,进一步对不同温度变化过程中的沉积差异进行探讨,揭示了盐类与风成砂的混合沉积形式能够反映气候变化。结果表明,温度影响盐类与风成砂混合沉积形式:①层状混合沉积:持续低温条件下(0~7℃),盐类晶体较粗厚度较大,与风成砂形成明显的韵律性层状混合沉积;②差异混合沉积:温度的连续变化(0~13℃)引起频繁的盐类在水面形成的薄膜状晶体在重力作用下崩塌,风成砂分布不均与盐类差异混合沉积。该认识为研究盐湖背景下混合沉积的形成机制提供了有价值的参考。